Functional Monomers and Polymers. 165. Dehydrochlorination of Head‐to‐Tail 1,4‐rans‐Poly‐(‐1‐Chlorobutadiene) Prepared by Inclusion Polymerization in Deoxycholic Acid Canals

Thermal and chemical dehydrochlorination of head‐to‐tail 1,4‐trans‐poly(‐1‐chlorobutadiene) prepared by inclusion polymerization in deoxycholic acid canals resulted in formation of a trans‐polyacetylene‐type polymer. The dehydrochiorinated polymer was characterized by UV/VIS, IR, Raman, and ESR spectroscopy. The number of conjugated double bonds in the polymer was about 10–20. Doping with iodine was also studied.     

Application of a newly developed portable NIR imaging device to monitor the dissolution process of tablets

We have recently developed a novel portable NIR imaging device (D-NIRs), which has a high speed and high wavelength resolution. This NIR imaging approach has been developed by utilizing D-NIRs for studying the dissolution of a model tablet containing 20 % ascorbic acid (AsA) as an active pharmaceutical ingredient and 80 % hydroxypropyl methylcellulose, where the tablet is sealed by a special cell. Diffuse reflectance NIR spectra in the 1,000 to 1,600 nm region were measured during the dissolution of the tablet. A unique band at around 1,361 nm of AsA was identified by the second derivative spectra of tablet and used for AsA distribution NIR imaging. Two-dimensional change of AsA concentration of the tablet due to water penetration is clearly shown by using the band-based image at 1,361 nm in NIR spectra obtained with high speed. Moreover, it is significantly enhanced by using the intensity ratio of two bands at 1,361 and 1,354 nm corresponding to AsA and water absorption, respectively, showing the dissolution process. The imaging results suggest that the amount of AsA in the imaged area decreases with increasing water penetration. The proposed NIR imaging approach using the intensity of a specific band or the ratio of two bands combined with the developed portable NIR imaging instrument, is a potentially useful practical way to evaluate the tablet at every moment during dissolution and to monitor the concentration distribution of each drug component in the tablet.

NMR-based characterization of a novel yellow chlorophyll catabolite, Ed-YCC,isolated from Egeria densa

A novel yellow chlorophyll catabolite, Ed-YCC, was isolated from leaves detached from Egeria densa shoots, in which chlorophyll degradation and anthocyanin synthesis were induced in 0.1 M fructose solution under light illumination as a plant senescence process, a model of autumnal leaf coloration. Structure elucidation was accomplished by various NMR techniques including 2D-INADEQUATE.     

Aqueous phase-synthesized small CdSe quantum dots: adsorption layer structure and strong band-edge and surface trap emission

We synthesized, in aqueous solution at room temperature, small water-soluble CdSe quantum dots (QDs) with strong photoluminescence (PL) and then correlated the PL with their adsorption layer structure. For synthesizing the QDs, their initial synthesis condition was controlled to form small Cd-containing species capable of passivating dangling bonds on the CdSe core surface. Each CdSe QD (d ~ 2.5 nm) consisted of a CdSe core (d ~ 2.1 nm), a cysteine (cys)-ligand shell, and an adsorption layer composed of Cd–cys complexes (mainly CdL(-H)⁻, cys ≡ H₂L), cys (as L²⁻), Cd(OH)₂, and CdO _x (x ≥ 1). Our CdSe QDs showed strong blue band-edge PL as well as strong green surface trap PL. Their PL quantum yield (QY) of ~18% was unexpectedly high, considering their extremely small core size and their absence of any wide-bandgap inorganic shell. We attributed the QY to their adsorption layer species. The small weakly charged Cd–cys complex and the small neutral cadmium oxides in the adsorption layer could relatively readily diffuse into the unprotected surface sites on the core. These wide-bandgap species coalesced selectively on the unprotected surface sites with minimal spatial disturbance to the preexisting surface Cd-ligand coordination, and passivated them effectively. These decreased nonradiative recombination of the excitons significantly and thus led to the unexpectedly high QYs.     

Fusarisetin A, an acinar morphogenesis inhibitor from a soil fungus, Fusarium sp. FN080326

An acinar morphogenesis inhibitor named fusarisetin A (1) that possesses both an unprecedented carbon skeleton and a new pentacyclic ring system has been identified from an in-house fractionated fungal library using a three-dimensional matrigel-induced acinar morphogenesis assay system. The structure of 1 was determined in detail by NMR and circular dichroism spectroscopy, X-ray analysis, and chemical reaction experiments.     

Enantioselective Discrimination of Alcohols by Hydrogen Bonding: A SERS Study

Efficient and generic enantioselective discrimination of various chiral alcohols is achieved by using surface‐enhanced Raman scattering (SERS) spectroscopy through charge–transfer (CT) contributions. The relative intensities of the peaks in the SERS spectra of a chiral selector are strongly dependent on the chirality of its surroundings. This highly distinct spectral discrepancy may be due to the tendency of chiral isomers to form intermolecular hydrogen‐bonding complexes with the chiral selector in different molecular orientations, resulting in different CT states and SERS intensities of the adsorbates in the system. This study opens a new avenue leading to the development of novel enantiosensing strategies. A particular advantage of this approach is that it is label‐free and does not employ any chiral reagents, including chiral light.     

New entry to the Pauson-Khand reaction: trimethylgermyl group at the triple bond terminus as a latent functional group

The Pauson-Khand reaction of enynes possessing a trimethylgermyl group at the alkyne terminus afforded the corresponding bicyclo[3.3.0]octenone and bicyclo[4.3.0]nonenone skeletons in a stereoselective manner. The resulting trimethylgermyl group of the bicyclic compounds was then converted to the iodo group, which was used for further elaboration. Thus, the trimethylgermyl group at the triple bond terminus was shown to be a precursor for other appendages.     

Biodegradations of block copolymers composed of L- or D,L-lactide and six-membered cyclic carbonates prepared with organolanthanide initiators

Diblock copolymerizations of L - or D,L -lactide (LA) with trimethylene carbonate (TMC) or 2,2-dimethyltrimethylene carbonate (2,2-DTMC) with SmMe(C₅Me₅)₂-(tetrahydrofuran) as an initiator and triblock copolymerizations of L - or D,L -LA/cyclic carbonates/L - or D,L -LA with [Sm(C₅Me₅)₂]₂(PhCCCCPh) as an initiator generated the desired block copolymers. This article describes the comparison of biodegradabilities by proteinase K and a compost and mechanical properties between the resulting di- or triblock copolymers and random copolymers composed of L - or D,L -LA and cyclic carbonates. The scanning electron microscopic profiles of resulting polymers were measured to understand the morphological change during biodegradation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3572–3588, 2003     

Laser Molding in Polymeric Materials Using Femto-Second Laser Pulse and Replication via Electroforming

The upheaval structure on the surface of polymer induced by the irradiation of a near-infrared (NIR) femto-second laser pulse in polymer bulk was investigated. Copolymers, such as poly(acrylonitrile-styrene) (AS) and poly(acrylonitrilebutadiene-styrene-methyl methacrylate) (ABSM) produced upheaval structures with a flattop just like the crater of a volcano, whereas homopolymers with relatively high glass transition temperature (T_g), such as polycarbonate (PC) and polyether imide (PEI) were more often formed a bell-shaped upheaval structure. A micro-lens effect was observed for the bell-shaped upheaval structure, but that effect was not observed in the case of copolymers with a flattop structure. Replication of the bell-shaped upheaval structure in PC was carried out by electroforming (non-electrolytic plating of Ni and the following electrolytic plating of Ni) and potting approximately 30 wt% THF solution of AS copolymer. A micro-scale bell-shaped upheaval structure in PC induced by a laser pulse was replicated using a Ni mother mold with suitable precision, and the replicated bell-shaped structure also showed a micro-lens effect.     

Polymer gel films with simple organic electrochromics for single-film electrochromic devices

Polymer gel films [poly(1-vinyl-2-pyrrolidinone-co-N,N′-methylenebisacrylamide) (PVPD)] which contain simple organic electrochromics [p-diacetylbenzene (p-DAB), dimethyl- or diethyl terephthalate (p-DMP or p-DEP)] are prepared and their optical responses to applied voltage are investigated. p-DAP/PVPD film is colored in green by the application of 1.2 V vs. Pt wire (quasireference electrode) across the film, and p-DMP/PVPD and p-DEP/PVPD films are colored in red by the application of ?2.5 and ?1.5 V vs. Pt, respectively. Their coloring responses are about a few seconds and the bleaching process also occurs rapidly. The films have no optical memory effect. © 1992 John Wiley & Sons, Inc.